Simplify the following expression: $n = \dfrac{8}{5x} - \dfrac{1}{4x}$
Answer: In order to subtract expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $5x$ and $4x$ $\lcm(5x, 4x) = 20x$ $ n = \dfrac{4}{4} \cdot \dfrac{8}{5x} - \dfrac{5}{5} \cdot \dfrac{1}{4x} $ $n = \dfrac{32}{20x} - \dfrac{5}{20x}$ $n = \dfrac{32 -5}{20x}$ $n = \dfrac{27}{20x}$